4. Which one of the following leads to the destruction of the ozone layer? A. release of carbon dioxide from the burning of fossil fuels
B. the release of CFC's found in refrigerants and aerosols
C. the production of acid rain
D. deforestation and habitat loss.

Which of the following best describes the purpose of the parathyroid hormone? a. it decreases the blood calcium level and decreases blood phosphorus level. b. it decreases the blood calcium level and increases the blood phosphorus level. c. it increases the blood calcium level and increases blood phosphorus level. d. it increases the blood calcium level and decreases blood phosphorus level.